CCD shift-alignment device for optical scanner

ABSTRACT

A device for holding a charge couple device (CCD) in an optical scanner where optical alignment of the CCD to the position of scanned image of document can be easily made. The device includes a holder for holding a lens and providing a focused image taken from the scanned document; and a positioning element mounted on the holder for adapting a CCD to be slightly moved in a line along a longitudinal direction of the CCD and aligned with the focused image. The positioning element is furnished with a matching hole for carrying a bottom portion of the CCD. The positioning element mounted to the holder only needs one-dimensional adjustment in shifting which is easier and more effective.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a positioning element for holding acharge couple device (CCD) in an optical scanner where optical alignmentof the CCD to the position of document image can be easily made.

2. Description of the Related Art

In an optical scanner, the image of a scanned document is reflected by anumber of mirrors focused by a lens, and imaged on a CCD, and thentransformed into digital signals for processing by a computer. In recentmanufacturing processes, the assembly of the lens and the CCD has beenincorporated into a module in which the lens and the CCD have to beadjusted and aligned into suitable optical positions in order to take asharp image from the document.

Two alignment methods of prior arts are as follows:

1) Electronic Method

As shown in FIG. 1A, an aligning arrangement for an optical scannerincludes a sample scale 10, a light source 12, four reflection mirrors14, a lens 16, and a CCD 18 mounted on a printed circuit board 24. Thearrangement corrects the alignment by checking the electronic wave ofscanning signals being transformed from the image of the scale 10 by theCCD 18, and adjusting the position of the CCD 18 relative to the lens16. In this way, the sample scale 10 is fixed, and the CCD 18 is to beadjusted.

2) Optical Method

As shown in FIG. 1B, an aligning arrangement for an optical scannerincludes the same of components of FIG. 1A: a sample scale 10, a lightsource 12, four reflection mirrors 14, a lens 16, and a CCD 18 mountedon a printed circuit board 24. The module of lens 16 and CCD 18 is firstsettled by using an optical instrument, such as a microscope, to adjustthe position of the CCD 18 relative to he lens 16 for a correctfocusing. In this way, the CCD 18 and the lens 16 are off-line adjusted.

No matter what method is utilized, the positioning of the CCD 18 has tobe provided with three degrees of freedom as illustrated in FIG. 2.

FIG. 2 shows a composition of a conventional lens and CCD module and itsalignment requirement. Firstly, a lens 16 mounted in a holder 20 on anaxes 22 is adjustable by using a driver 23 to move inward or outwardsfor focusing on a CCD 18. Since the CCD 18 has been soldered on a PCB(Printed Circuit Board) 24, we have to adjust the PCB 24 in movements ofX-direction, Z-direction and Y-rotation as illustrated in order to aligna scanned image on the optoelectronic elements 47 before fastening thePCB 24 to the holder 20 with two screws 28 movable in two slots 26.Because the adjustment has to be done in aforesaid three degrees offreedom, and it is complicated, time consuming, and eventually difficultto achieve a reliable alignment.

SUMMARY OF THE INVENTION

It is therefore a primary objective of the present invention to solvethe problems of CCD alignment encountered in prior arts and provide anew simplified device.

The present invention discloses a positioning element that holds a CCDin a manner of accurately positioning the optoelectronic elements of theCCD relative to the positioning element which mounts to a holder thatincorporates the lens and the CCD. The positioning element mounted tothe holder only needs one-dimensional adjustment in shifting which iseasier and more effective.

The other objectives and features of the present invention will becomeapparent from the following description of preferred embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a prior art schematic view showing an alignment arrangementfor an optical scanner in which an electronic method is used.

FIG. 1B is a prior art schematic view showing an alignment arrangementfor an optical scanner in which an optical method is used.

FIG. 2 is an exploded view showing the composition of a conventionallens and CCD module and the alignment requirement thereof.

FIGS. 3A, 3B, and 3C illustrate respectively a document to be scanned, acomposition of a scanner, and the scanned image.

FIGS. 4A, 4B, and 4C illustrate respectively the top view, the frontview and the side view of a packaged CCD of prior arts.

FIGS. 5A and 5B illustrate respectively the top view and the sectionalfront view of a positioning element for CCD according to the presentinvention.

FIGS. 6A, 6B, and 6C illustrate respectively a horizontal sectionalview, a vertical sectional view, and a front view of a first embodimentof the present invention.

FIGS. 7A, 7B, and 7C illustrate respectively a horizontal sectionalview, a vertical sectional view, and a front view of a second embodimentof the present invention.

FIG. 8 is an exploded view showing the composition of a positioningdevice according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As in the above description, FIGS. 1A, 1B, and FIG. 2 illustratealignment methods for optical scanner of prior arts.

Further referring to FIGS. 3A, 3B, and 3C, a document 30 is scanned by ascanner that includes a light source 12, at least one reflection mirror14, a lens 16, and a CCD 18. If all the optical elements aligns well,the scanned image of an original line "a" focused by the lens 16 andprojected on the CCD 18 is shown in FIG. 3C as image "a" or, undermisalignment, a bias image "b" or "c". So the scanner elements, i.e. thereflection mirror 14, the lens 16, and the CCD 18, have to be aligned oradjusted. Especially, the CCD 18 has to be aligned to the focused image"a", "b" or "c". Practically, the angular variance as of the image "b"or "c" can be controlled in an acceptable range by careful arrangementof the optical elements. The problem left is only the left-rightadjustment that ensures the image "a", "b" or "c" to fall into theregion of CCD 18.

As described in FIG. 2 of prior arts, since the CCD 18 has been solderedon a PCB 24 without any alignment constraint during the solderingprocess, we have to adjust the PCB 24 in movements of three degrees offreedom in order to achieve image alignment of the CCD. Because theadjustment of aforesaid three degrees of freedom is complicated, timeconsuming, and eventually difficult, the present invention intends tosimplify the alignment process by controlling the mounting position ofthe CCD relative to the lens.

The present invention discloses a positioning element that holds a CCDin a manner of accurately positioning the optoelectronic elements of theCCD relative to the positioning element which mounts to a holder thatincorporates the lens and the CCD. The positioning element mounted tothe holder needs only one-dimensional adjustment in shifting which iseasier and more effective.

Referring to FIGS. 4A, 4B, and 4C, it is shown the top view, the frontview, and the side view of a packaged CCD 18 of prior arts. During thepackaging process, the bottom portion 42 of the package is based on thepins 46, i.e. the optoelectronic element 47 of the CCD 18, and thevariance of configuration is generally between 0.3 mm only (the varianceof the top portion 44 is larger than that). So it is possible to use theedge 45 of the bottom portion 42 as a positioning base when mounting theCCD 18 to a PCB or a positioning element.

Now referring to FIGS. 5A and 5B, it is shown the top view and thesectional front view of a positioning element for CCD according to thepresent invention. The positioning element 52 is made of plastics orother insulating materials. A matching hole 54 furnished on the element52 for carrying the bottom portion 42 of a CCD 18 makes theoptoelectronic element 47 of the CCD precisely aligned with thepositioning element 52. The element 52 is preferred of a square block asshown. The function of the positioning element 52 will be describedbelow.

Referring now to FIGS. 6A, 6B, and 6C, a horizontal sectional view, avertical sectional view and a front view of a first embodiment of thepresent invention in which a positioning element 52 for a CCD 18fastened to a CCD and lens holder 20 is shown. The holder 20 is a closedmember that incorporates a lens 16 at an opening and a CCD 18 at anotheropening faced to the lens 18. The CCD 18 is soldered on a PCB 24 to befastened to the holder 20 by some fastening means such as screws 28. Apositioning element 52 firmly holds the CCD 18 in a relative accurateposition as described in FIGS. 5A and 5B. The CCD 18 and the positioningelement 52 can be bonded together or fixed to the PCB 24. There areseveral positioning portions 62 (four portions shown in FIG. 6B whichmay be reduced to three on triangular positions) furnished on the innersurface of the holder 20 for guiding the positioning element 52 movableonly in left-right direction as-changing the clearances X1 and X2. Asillustrated in FIG. 6C, two slots 26 are furnished on the PCB 24 for twoscrews 28 passing through and fastening the PCB 24 to the holder 20after adjusting the left-right alignment of the CCD 18.

FIGS. 7A, 7B, and 7C illustrate a second embodiment of the presentinvention similar to the first one of FIGS. 6A, 6B, and 6C but modifiedin the guiding portion of the holder 20. The positioning element 52 isguided in the holder 20 by its side surfaces 502 sliding on the innersurfaces 200 of the holder 20.

FIG. 8 is an exploded view showing the composition of a positioningdevice similar to the aforesaid embodiments with two additional slots 26furnished on the positioning element 52 for the screws 28 to pass themthrough fastening the element 52 with the PCB 24 and the holder 20.

It is apparent to those skilled in the art that various changes may bemade without departing from the scope of the invention disclosed.

What is claimed is:
 1. A device for aligning a charge coupled device(CCD) to a scanned image position in an optical scanner, comprising:aholder for holding a lens and a CCD, and producing a focused image takenfrom a scanned document on said CCD; a bottom portion affixed to saidCCD, said bottom portion having truncated edges such that its widthdecreases linearly with distance from said CCD; a positioning elementaffixed to said holder; an opening formed in said positioning elementfor receiving said bottom portion, said opening having matchingtruncated edges so as to allow said bottom portion to be receivedtherein without clearance therebetween and restrict movements of saidCCD; and linear adjustment means provided with said positioning elementto allow for only one directional adjustment of said positioning elementrelative to said holder before said positioning element is fixed to saidholder.
 2. A device according to claim 1 wherein said CCD is soldered ona printed circuit board, said positioning element is held between saidprinted circuit board and said holder for fixing said CCD.
 3. A deviceaccording to claim 1 wherein said CCD is bonded to said opening of saidpositioning element.
 4. A device according to claim 2 wherein saidpositioning element is furnished with two sides parallel to alongitudinal direction of said positioning element for moving along twoinner sides of said holder for CCD alignment, and fastened with said PCBto said holder by fastening means.
 5. A device according to claim 4wherein said inner sides of said holder is furnished with a plurality ofguiding portions for guiding said positioning element.
 6. A deviceaccording to claim 4 wherein at least one of said PCB and saidpositioning element is furnished with slots laid parallel to saidlongitudinal direction of said positioning element for screws passingthrough and fastening them to said holder after CCD alignment.
 7. Adevice according to claim 1 wherein said positioning element is mountedwithin a frame-shaped plate, which is then affixed to said holder, andsaid linear adjustment means comprises a plurality of protrusions fromtwo opposing inner sides of said frame-shaped plate, said protrusionscollectively urging said positioning element so as to allow saidpositioning element to move in only one direction.
 8. A device accordingto claim 1 wherein said positioning element is mounted within aframe-shaped plate, which is then affixed to said holder, and saidlinear adjustment means comprises a tight fit between said positioningelement and said frame-shaped plate at first opposing inner sides but afinite clearance at second opposing sides so as to allow saidpositioning element to move in only one direction.